• Economic and Environmental Geology
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• v.57 no.1
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• pp.17-23
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• 2024

Ground penetrating radar (GPR) survey is a geophysical method that utilizes electromagnetic waves reflecting from a boundary where the electromagnetic property changes. As the frequency of the antenna is about 25 MHz ~ 1 GHz, it is effective to acquire high resolution images of underground pipe, artificial structure, underground cavity, and underground structure. In this study, we analyzed the change of signals reflected from the same underground objects according to the arrangement of transceiver antennas used in ground penetrating radar survey. The antenna used in the experiment was 200 MHz, and the survey was performed in the vertical direction across the sewer and the parallel direction along the sewer to the sewer buried under the road, respectively. A total of five antenna array methods were applied to the survey. The most used arrangement is when the transmitting and receiving antennas are all perpendicular to the survey line (PR-BD). The PR-BD arrangement is effective when the object underground is a horizontal reflector with an angle of less than 30°, such as the sewer under investigation. In this case study, it was confirmed that the transmitter and receiver antennas perpendicular to the survey line (PR-BD) are the most effective way to show the underground structure. In addition, in the case where the transmitting and receiving antennas are orthogonal to each other (XPOL), no specific reflected wave was observed in both experiments measured across or parallel to the sewer. Therefore, in the case of detecting undiscovered objects in the underground, the PR-BD array method in which the transmitting and receiving antennas are aligned in the direction perpendicular to the survey line taken as a reference and the XPOL method in which the transmitting and receiving antennas are orthogonal to each other are all used, it can be effective to apply both of the above arrangements after setting the direction to 45° and 135°.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.182.2-182.2
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• 2010

A various algorism has been studied to extract possibly every energy from a wind turbine in conjunction with the increase of concern about wind power system. In order to verify these control algorism, it is essential to make the most similar conditions to the real wind turbine's environment. Therefore, using separately excited DC motor a wind turbine the most similar to the real turbine is simulated. Tower shadow effect and Wind shear effect are considered as well as inertia emulation. For the control of Back-to-Back Converter Vector current control methods and space vector pulse width modulation are used and for reducing THD of grid current LCL filter is considered. This simulation results verified the energy produced by wind all flows into the utility under the consideration of the characteristics of a wind turbine. The result of this paper is expected to be used as a basic material for analyzing the characteristics of the wind turbine generator.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.53 no.1
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• pp.32-39
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• 2004

The color-based vision systems have been used to recognize our team robots, the opponent team robots and a ball in the robot soccer system. The color-based vision systems have the difficulty in that they are very sensitive to color variations brought by brightness changes. In this paper, a neural network trained with data obtained from various illumination conditions is used to classify colors in the modified YUV color space for the robot soccer vision system. For this, a new method to measure brightness is proposed by use of a color card. After the neural network is constructed, a look-up-table is generated to replace the neural network in order to reduce the computation time. Experimental results show that the proposed color classification method is robust under illumination variations.

• Water Engineering Research
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• v.5 no.2
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• pp.81-99
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• 2004

Long term streamflow regime under virtual climate change scenario was examined. Rainfall forecast simulation of the Canadian Global Coupled Model (CGCM2) of the Canadian Climate Center for modeling and analysis for the IPCC SRES B2 scenario was used for analysis. The B2 scenario envisions slower population growth (10.4 billion by 2010) with a more rapidly evolving economy and more emphasis on environmental protection. The relatively large scale of GCM hinders the accurate computation of the important streamflow characteristics such as the peak flow rate and lag time, etc. The GCM rainfall with more than 100km scale was downscaled to 2km-scale using the space-time stochastic random cascade model. The HEC-HMS was used for distributed hydrologic model which can take the grid rainfall as input data. The result illustrates that the annual variation of the total runoff and the peak flow can be much greater than rainfall variation, which means actual impact of rainfall variation for the available water resources can be much greater than the extent of the rainfall variation.

• Journal of applied mathematics & informatics
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• v.16 no.1_2
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• pp.1-17
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• 2004

The famous Newton-Kantorovich hypothesis has been used for a long time as a sufficient condition for the convergence of Newton method to a solution of an equation in connection with the Lipschitz continuity of the Frechet-derivative of the operator involved. Using Lipschitz and center-Lipschitz conditions we show that the Newton-Kantorovich hypothesis is weakened. The error bounds obtained under our semilocal convergence result are finer and the information on the location of the solution more precise than the corresponding ones given by the dominating Newton-Kantorovich theorem, and under the same hypotheses/computational cost, since the evaluation of the Lipschitz also requires the evaluation of the center-Lipschitz constant. In the case of local convergence we obtain a larger convergence radius than before. This observation is important in computational mathematics and can be used in connection to projection methods and in the construction of optimum mesh independence refinement strategies.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.526-544
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• 2021

Based on the potential flow theory, a fully nonlinear numerical procedure is developed with boundary element method to analyze the interaction between a fixed semi-submersible platform and incident waves in open water. The incident wave is separated from the scattered wave under fully nonlinear boundary conditions. The mixed Euler-Lagrangian method is used to capture the position of the disturbed wave surface in local coordinate systems. The wave forces exerted on an inverted conical frustum are used to ensure the accuracy of the present method and good agreements with published results are obtained. The hydrodynamic characteristics of the semi-submersible platform interacting with regular waves are analyzed. Pressure distribution with time and space, tension and compression of the platform under wave action are investigated. 3D behaviors of wave run-ups are predicted. Strong nonlinear phenomena such as wave upwelling and wave interference are observed and analyzed.

• Journal of the Korean Institute of Rural Architecture
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• v.12 no.4
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• pp.21-28
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• 2010

As the issues such as safety, hygiene, convenience of school facility from the perspective of living environment for students and teachers arise as an important task in recent, there is increasing concern for resting convenience facility in school. In recent, the government is planning to change middle high school into the departmental classroom system. The departmental classroom system refers to the school operation system in which the classroom is structured as a subject-specialized classroom and the students move to the classroom according to their class schedules. This departmental classroom system is advantageous in that each subject can be equipped with professional facilities or preparations; the usage rate of the classroom can be enhanced; the common study space or living space can be used substantially; the school can plan and operate its own specialized space. On the contrary, it has the weaknesses that there is need to prepare the home base for the guidance of the class or student guidance; there is need for the facilities including personal lockers. Thus, the departmental classroom system requires the space expansion for home base or the resting convenience space for students and thus has to provide various spaces. Under this background, it is also important to check and plan the resting space for the schools. Therefore, this study is aimed to examine and analyze the arrangement location and space Layout of the resting convenience space among school facilities to propose the architectural data for future resting/convenience spaces for the schools.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.11
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• pp.849-859
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• 2020

The semi-empirical equation and commercial computational tool were used to predict the base drag of a guided missile with free-stream Mach numbers and chamber pressures, and the results were generally agree each other. Differences in flow characteristics and base drags were observed with over/under expansion conditions by the nozzle. Under the over-expansion condition, the base pressure decreased as the expansion fan was generated at upper region of the base, and base pressure decreased further with increasing free-stream Mach number as the expansion becomes strong. Under the under-expansion conditions, a shock wave was generated around the base by the influence of the nozzle flow, which increased the base pressure, and the effect increased as the chamber pressure increased. Under the same chamber pressure condition, as the free-stream Mach number increases, the characteristic that the base pressure decreases as the shock wave generated at the base moves downstream was observed.

• Journal of the Korean housing association
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• v.21 no.4
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• pp.71-79
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• 2010

This study is a fundamental research which suggests some standards that can be used in selecting some advanced materials to be applied in housing space designs. The following conclusions have been drawn from the study. First, it has been discovered that as the residents' quality of life improved, the finishing materials emerged as an important element of housing spaces. It could also be seen that among the finishing materials used in housing spaces, there is recently a growing trend towards various environmentally-friendly advanced materials under the theme of 'the nature' and 'health'. As a result, the need to investigate the standards of discriminatory and efficient housing space designs using advanced materials is on the increase. Second, through the literature and precedent studies, the physical criteria of advanced materials have been classified into five categories: new technology, new manufacturing methods, new materials, complementation and applicability. The main criteria of advanced finishing materials for housing spaces have been classified into four main categories: durability, functionality, economical efficiency and sensibility. By collecting and classifying some key words according to each of these four categories, the representative or combinable features have been extracted. By organizing the advanced materials' physical criteria and their details, some standards based on the physical aspects have been suggested. The features of the finishing materials in consideration of advanced materials have been reclassified into the user-based criteria, environmental criteria and spatial criteria. Through this method, the criteria have been brought up from a new viewpoint, establishing the standards for the advanced materials applicable to housing spaces. Finally, after assessing the criteria by analyzing the advanced materials currently known to be applicable in housing spaces, it has been concluded that the criteria can be used as the fundamental standards. As this study is based on investigating the literature and data, it may be less than reasonable to generalize from the limited number of examples. Hence, it shall be important to make a profound study of some detailed criteria by suggesting more objective standards and analyzing a greater variety of advanced materials.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.3
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• pp.270-278
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• 2014

This paper describes an improvement of space objects orbit prediction. To screen possible collisions between operational satellites and space objects, the TLE (Two-Line Element) was used as pseudo-measurement and than the orbit determination and orbit prediction were performed through the flight dynamics system. For determining the orbits, the state vectors were assumed by a series of TLEs within a certain period. The propagation error was analyzed according to the fitting period and a number of pseudo-observations. In order to find out the improvement of orbit prediction with the proposed method, KOMPSAT-2, 3 having the precise orbit in the meter-level range were first applied. Then the result applied to space objects under the same conditions was analyzed. As a result of the RMS error comparison with the orbit prediction of space object, the precision of orbit prediction was improved by approximately 90% for seven days prediction. The improved orbit prediction of space objects can be utilized in the daily analysis for initial screening of the close space objects at high risk.